Chip resistor and method for manufacturing same

ABSTRACT

A chip resistor (R 1 ) includes a resistor element ( 1 ) having a first surface ( 1   a ) and a second surface ( 1   b ) opposite to the first surface. Two main electrodes ( 21 ), spaced from each other, are provided on the first surface ( 1   a ), while two auxiliary electrodes ( 22 ), spaced from each other, are provided on the second surface ( 1   b ). The auxiliary electrodes face the main electrodes ( 21 ) via the resistor element ( 1 ). The main electrodes ( 21 ) and the auxiliary electrodes ( 22 ) are made of the same material.

TECHNICAL FIELD

The present invention relates to a chip resistor and a method of makingthe same.

BACKGROUND ART

FIGS. 10 and 11 illustrate a conventional chip resistor. The chipresistor 1A shown in FIG. 10 is disclosed in JP-A-2002-57009, and thechip resistor 2A shown in FIG. 11 is disclosed in JP-A-2002-57010.

As shown in FIG. 10, the chip resistor 1A includes a metal resistorelement 100 and a pair of copper electrodes 110. The electrodes 110 arefixed to a lower surface 100 a of the resistor element 100 and spacedfrom each other in the direction X in the figure. Each of the electrodes110 includes a lower surface provided with a solder layer 130.

The chip resistor 1A is surface-mounted on e.g. printed circuit board,using solder. It is desirable that melted solder uniformly contacts withthe entire lower surface of each of the electrode 110. However, themelted solder may contact only with an inner surface 111 and itsvicinity of the electrode 110. The melted solder may also contact withonly an outer surface 112 of the electrode 110. The chip resistor 1A mayprovide different resistances in the former case and in the latter case.Thus, a circuit using the chip resistor 1A may not have a desirableelectrical property depending on the soldering condition. Suchdisadvantage is noticeable especially in a chip resistor having a lowresistance (not more than 100 mΩ for example).

The chip resistor 2A shown in FIG. 11 includes a pair of bonding pads120 in addition to the features of the above-described chip resistor 1A.Specifically, the two bonding pads 120 are fixed to an upper surface 100b of the resistor element 100 and spaced from each other in thedirection X. As shown, each of the bonding pads 120 is arranged rightabove a respective one of the electrodes 110. The bonding pad 120 ismade of a material suitable for wire bonding such as nickel, and has aspecific resistance lower than that of the resistor element 100.

In the chip resistor 2A with the above structure, the resistance islower at each end portion (i.e. the aggregate portion consisting of anelectrode 110, a bonding pad 120, and an end region of the resistorelement 110 that is sandwiched by the former two components) than whenthe bonding pad 120 is not provided (see the chip resistor 1A shown inFIG. 10). Accordingly, the above-described disadvantage of the chipresistor 1A can be reduced or practically eliminated in the chipresistor 2A.

However, in the chip resistor 2A shown in FIG. 11, the electrodes 110are made of copper, while the bonding pads 120 are made of nickel, forexample. Thus, two different materials must be prepared for forming theelectrodes and the bonding pads. Further, the electrodes 110 and thebonding pads 120, which are made of different materials, must be formedin different process steps. As a result, the product cost of the chipresistor 2A is disadvantageously increased.

DISCLOSURE OF THE INVENTION

The present invention has been proposed under the above-describedcircumstances. It is therefore an object of the present invention toprovide a chip resistor whose resistance difference due to the solderingcondition is small and whose product cost can be reduced. Further, it isanother object of the present invention to provide a method of makingsuch chip resistor.

A chip resistor according to a first aspect of the present inventioncomprises: a resistor element including a first surface and a secondsurface opposite to the first surface; at least two main electrodesspaced from each other and provided on the first surface; and at leasttwo auxiliary electrodes spaced from each other and provided on thesecond surface. The auxiliary electrodes are arranged to face the mainelectrodes via the resistor element. The main electrodes and theauxiliary electrodes are made of the same material.

Preferably, the spacing distance between the auxiliary electrodes is nosmaller than the spacing distance between the main electrodes.

Preferably, the chip resistor according to the present invention furthercomprises a first insulating layer and a second insulating layer thatare formed on the resistor element. The first insulating layer covers anarea between the main electrodes on the first surface of the resistorelement, while the second insulating layer covers an area between theauxiliary electrodes on the second surface of the resistor element.

Preferably, the thickness of the first insulating layer is no greaterthan the thickness of the main electrodes.

Preferably, the chip resistor according to the present invention furthercomprises at least two solder layers formed on the resistor element. Theresistor element includes a pair of end surfaces spaced from each other,and each of the end surfaces is covered by a corresponding one of thetwo solder layers.

Preferably, the solder layers cover the main electrodes and theauxiliary electrodes in addition to the end surfaces of the resistorelement.

Preferably, the chip resistor according to the present invention furthercomprises a third insulating layer formed on the resistor element. Theresistor element includes a side surface extending between the firstsurface and the second surface. The side surface is covered by the thirdinsulating layer.

A method of making a chip resistor according to a second aspect of thepresent invention comprises the steps of: preparing a resistor materialincluding a first surface and a second surface opposite to the firstsurface; forming a pattern of first conductive layer on the firstsurface; forming a pattern of second conductive layer on the secondsurface; and dividing the resistor material into a plurality of resistorelements. The first and second conductive layers are made of the samematerial.

Preferably, the dividing of the resistor material is performed in amanner such that a resulting chip resistor comprises a main electrodemade of a part of the first conductive layer and also comprises anauxiliary electrode made of a part of the second conductive layer.

Preferably, the method of making chip resistor according to the presentinvention further comprises an additional step, performed before thepattern forming of the first conductive layer, for forming a pattern ofa first insulating layer on the first surface of the resistor materialand also a pattern of a second insulating layer on the second surface ofthe resistor material. The first conductive layer and the secondconductive layer are formed on areas of the resistor material where thefirst and the second insulating layers are not formed.

Preferably, the pattern forming of the insulating layer is formed bythick-film printing.

Preferably, the first and the second conductive layers are formed bymetal plating.

Preferably, the resistor material is divided by punching or by cutting.

Preferably, the method of making a chip resistor according to thepresent invention further comprises the steps of; forming an insulatinglayer on a side surface of each resistor element; and forming a solderlayer on an end surface of the resistor element by barrel-plating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a chip resistor according tothe present invention.

FIG. 2 is a section view taken along lines II-II of FIG. 1.

FIGS. 3A-3C are views illustrating process steps of a method of makingthe chip resistor.

FIGS. 4A-4B are views illustrating process steps following the processstep shown in FIG. 3C.

FIGS. 5A-5B are views illustrating process steps following the processstep shown in FIG. 4B.

FIG. 6 is a perspective view illustrating a modified example of the chipresistor shown in FIG. 1.

FIG. 7A is a perspective view illustrating an example of a frame formaking the chip resistor according to the present invention, and FIG. 7Bis a plan view illustrating a principal part of the frame.

FIGS. 8A-8B are views illustrating an example of production methodutilizing the frame.

FIGS. 9A-9B are views illustrating another example of production methodutilizing the frame.

FIG. 10 is a perspective view illustrating an example of a conventionalchip resistor.

FIG. 11 is a perspective view illustrating another example of aconventional chip resistor.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention is described below withreference to the accompanying drawings.

FIGS. 1 to 2 illustrate a chip resistor according to the presentinvention. The illustrated chip resistor R1 includes a resistor element1, a pair of main electrodes 21, a pair of auxiliary electrodes 22,first and second insulating layers 31, 32, and a pair of solder layers4.

The resistor element 1 is a rectangular chip made of a metal and has aconstant thickness. Examples of material for forming the resistorelement 1 include Ni—Cu alloy or Cu—Mn alloy, though not limited tothese. The material of the resistor element 1 may be selected frommaterials having a resistivity suited to provide the chip resistor R1with an intended resistance.

The pair of main electrodes 21 and the pair of auxiliary electrodes aremade of a same material such as copper, for example. Each of the mainelectrodes 21 is formed on a lower surface 1 a of the resistor element1, while each of the auxiliary electrodes 22 is formed on an uppersurface 1 b of the resistor element 1. The paired main electrodes 21 arespaced from each other in a direction X shown in the figures, and so arethe paired auxiliary electrodes 22. Each main electrode 21 and eachauxiliary electrode 22 includes an outside surface 21 a or 22 a, whichis flush with one of end surfaces 1 c (the end surfaces spaced from eachother in the direction X) of the resistor 1. As shown in FIG. 2, thewidth w1 of each main electrode 21 is larger than the width w2 of eachauxiliary electrode 22, while the spacing S1 between the pair of mainelectrodes 21 is smaller than the spacing S2 between the pair ofauxiliary electrodes 22.

The first and second insulating layers 31, 32 are all made of a resinsuch as epoxy resin. The first insulating layer 31 is formed on thelower surface 1 a of the resistor element 1, at an area between the mainelectrodes 21. In a similar way, the second insulating layer 32 isformed on the upper surface 1 b of the resistor element 1, at an areabetween the auxiliary electrodes 22. A pair of side ends 31 a of thefirst insulating layer 31 are spaced in the direction X, each contactingwith an inside surface 21 b of respective main electrode 21. Similarly,a pair of side ends 32 a of the second insulating layer 32 are spaced inthe direction X, each touching an inside surface 22 b of respectiveauxiliary electrode 22. Thus, the spacing S1 between the pair of mainelectrodes 21 is equal to the width of the first insulating layer 31,and the spacing S2 between the pair of auxiliary electrodes 22 is equalto the width of the second insulating layer 32. The thickness t3 of thefirst insulating layer 31 is smaller than the thickness t1 of the mainelectrodes 21, and the thickness t4 of the second insulating layer 32 issmaller than the thickness t2 of the auxiliary electrodes 22. However,this is not limitative for the present invention, but the thickness t3and t1 may be the same, and the thickness t4 and t2 may also be thesame.

As can be seen from FIGS. 1 and 2, each of the solder layers 4 includesa bottom portion (covering the main electrode 21), a top portion(covering the auxiliary electrode 22), and a side portion connecting thebottom and the top portions. The side portion covers the end surface 1 cof the resistor 1. The solder layer 4 is formed through plating, asdescribed below. Thus, as indicated by reference signs n1, n2 in FIG. 2,the solder layer 4 is elongated over a part of each of the first andsecond insulating layers 31, 32. Similarly to the solder layer 4, themain electrodes 21 and the auxiliary electrodes 22 are also formedthrough plating. Thus, though not shown, the main electrodes 21 and theauxiliary electrodes 22 actually overlap respective one of the firstinsulating layer 31 and the second insulating layer 32.

The resistor element 1 has a thickness of about 0.1 mm-1.0 mm. Each ofthe main electrodes 21 and the auxiliary electrodes 22 has a thicknessof about 30 μm-200 μm. Each of the first and second insulating layers31, 32 has a thickness of about 20 μm. The solder layer 4 has athickness of about 5 μm. Each of the length and the width of theresistor element 1 may be about 2 mm-7 mm. Of course, these dimensionsare only exemplary. For example, dimensions of the resistor element 1may be decided according to an intended resistance. The chip resistor R1is intended to have a low resistance (e.g. about 0.5 mΩ-100 mΩ).

The above-described chip resistor R1 may be made by a method shown inFIGS. 3-5.

First, as shown in FIG. 3A, a metal plate 10 is prepared for making theresistor 1. The plate 10 has dimensions (length multiplied by width)large enough to make a plurality of the resistors 1, and also has aconstant thickness as a whole. The plate 10 includes a first surface 10a and a second surface 10 b opposite to the first surface.

As shown in FIG. 3B, a plurality of strip-shaped insulating layers 31′are formed on the first surface 10 a of the plate 10. The insulatinglayers 31′ are elongated in parallel to each other, and spaced from eachother at a predetermined distance. The insulating layer 31′ may beformed by thick-film printing using e.g. epoxy resin.

As shown in FIG. 3C, a plurality of strip-shaped insulating layers 32′is formed on the second surface 10 b of the plate 10. The insulatinglayers 32′ are elongated in parallel to each other, and spaced from eachother at a predetermined distance. Preferably, similarly to theabove-described insulating layer 31′, the formation of the insulatinglayer 32′ may be formed by thick-film printing using epoxy resin. By thesame method using the same resin, the product cost can be reduced byforming the insulating layers 31′, 32′. Further, by the thick-filmprinting, the width and the thickness of each insulating layers 31′, 32′can be accurately formed in predetermined dimensions. As shown in thefigure, each of the insulating layers 32′ is vertically formed andpositioned relative to a respective one of the insulating layer 31′, andthe width of the insulating layer 32′ is larger than the width of theinsulating layer 31′.

As shown in FIG. 4A, on the first surface 10 a, first conductive layers21′ are further formed between the insulating layers 31′. At the sametime, on the second surface 10 b, second conductive layers 22′ areformed between the insulating layers 32′. The conductive layers 21′, 22′are formed by e.g. copper-plating. The conductive layers 21′ are toserve as the main electrodes 21, and the conductive layers 22′ are toserve as the auxiliary electrodes 22.

Due to the plating process, a plurality of conductive layers each havingconstant thickness can be formed simultaneously and easily. Further, theplating process enables the formation of the conductive layers withoutcausing spaces between the conductive layers and the insulating layers.

As shown in FIG. 4B, after the conductive layers 21′, 22 are formed, theplate 10 (and the conductive layers 21′, 22 formed thereon) is cut alongimaginary lines C1. Each of the cutting lines is located at such aposition as to halve a respective one of the conductive layers 21′, 22′widthwise thereof. This cutting process divides the plate 10 into aplurality of bar-shaped resistor material bodies 1′. Each of theresistor material bodies 1′ includes a pair of side surfaces 1 c′ whichare the cut surfaces elongated lengthwise of the resistor material.

As shown in FIG. 5A, the side surfaces 1 c′ of the resistor materialbodies 1′ and the conductive layers 21′, 22′ are covered by solderlayers 4′. Here, a bar-shaped resistor aggregate R1′ is obtained. Thesolder layer 4′ is formed through plating, for example.

As shown in FIG. 5B, the resistor aggregate R1′ is cut along imaginarylines C2. Each of the cutting lines is spaced from each other at apredetermined distance in length of the resistor aggregate R1′. Thiscutting process divides the resistor aggregate R1′ into a plurality ofthe chip resistor R1.

The chip resistor R1 made in above-described method may besurface-mounted on a circuit board (or another target mount) by reflowsoldering, for example. Specifically, In reflow soldering, a solderpaste is applied onto terminals of the circuit board. Thereafter, thechip resistor R1 are placed on the circuit board so that the mainelectrodes 21 contact with the solder paste. In this state, the circuitboard and the chip resistor R1 are heated in a reflow furnace. Finally,the chip resistor R1 is fixed to the circuit board upon cooling forsolidification of melted solder.

The solder layers 4 are melted during the reflow soldering. The solderlayers 4 are formed on the end surfaces 1 c of the resistor element 1 aswell as on the surfaces of the main electrodes 21 and auxiliaryelectrodes 22. Thus, the melted solder forms solder fillets Hf, asindicated by imaginary lines in FIG. 1. The state (e.g. shape) of thesolder fillets Hf may be checked from outside for determining whetherthe mounting of the chip resistor R1 is appropriate. The solder filletsHf facilitate reliable mounting of the chip resistor R1 on the circuitboard. Further, the solder fillets Hf radiate the heat caused at thechip resistor R1, and thus regulate a temperature rise of the chipresistor R1. In order to form such solder fillets Hf, each of the solderlayers preferably includes the bottom portion (covering the mainelectrode 21), the side portion (covering the side end 1 c of theresistor element 1), and the top portion (covering the auxiliaryelectrode 22), though this is not limitative on the present invention.For example, the solder layer 4 may include at least the portioncovering the side end 1 c of the resistor element 1. Preferably, thebottom, side, and top portions of the solder layer 4 are integrated,though the three portions may be separated from each other.

In surface-mounting of the chip resistor R1, the melted solder may flowapart from the main electrodes 21 and auxiliary electrodes 22. Theinsulating layers 31, 32 are formed on a “non-electrode area” (where themain electrode 21 and the auxiliary electrode 22 are not formed) of thelower surface 1 a and the upper surface 1 b of the resistor element 1.Due to this structure, the melted solder is prevented from directlysticking to the resistor element 1.

In order for the chip resistor R1 to have an intended resistance(resistance between the pair of main electrodes 21), it is necessary toaccurately set the spacing S1 between the pair of main electrodes 21 ata predetermined value. In this regard, the spacing S1 between the pairof main electrodes 21 is determined by the first insulating layer 31whose size can be accurately set by thick-film printing. Thus, it ispossible to accurately set the spacing S1 at a predetermined value.

Each of the auxiliary electrodes 22 made of copper has a high electricconductivity equal to that of the main electrodes 21. The auxiliaryelectrode 22 has a specific resistance lower than that of the resistorelement 1. Thus, the electric resistance is lower, at an area includingthe main electrodes 21, the auxiliary electrodes 22, and a portion ofthe resistor element 1 sandwiched by the electrodes, than the electricresistance at a resistor element which is not provided with theauxiliary electrode 22 (see FIG. 10). This results in reduction of adifference between the resistance values in cases where the soldercontacts with the under surfaces of the main electrodes 21 a only at aportion adjacent to each inside surface 21 b, and where the soldercontacts with the under surfaces of the main electrodes 21 a only at aportion adjacent to each outside surface 21 a.

The spacing S2 between the auxiliary electrodes 22 is larger than thespacing S1 between the main electrodes 21. Thus, the resistance betweenthe auxiliary electrodes 22 is larger than the resistance between themain electrodes 21. Therefore, the resistance between the auxiliaryelectrodes 22 does not cause drop of the resistance of the chip resistorR1 to below the desired resistance value.

Each of the main electrodes 21 and the auxiliary electrodes 22 partiallyoverlaps a respective one of the side ends 31 a, 32 a of the first andsecond insulating layers 31, 32. Therefore, the side ends 31 a, 32 a areprevented from easily coming off the resistor element 1.

The present invention is not limited to the above-described embodiment.The specific components of the chip resistor according to the presentinvention may be modified in various ways. Similarly, the specificprocess steps of the method of making the chip resistor according to thepresent invention may be modified in various ways.

For example, the chip resistor according to the present invention may bedesigned as shown in FIG. 6. In FIG. 6 and the following figures,elements identical to or similar to those in the above-describedembodiment are given the same reference numbers.

The chip resistor R2 shown in FIG. 6 is provided with a pair of thirdinsulating layers 33 covering a pair of side surfaces 1 d of theresistor element 1. Due to this structure, the solder is prevented fromsticking to the side surfaces 1 d of the resistor element 1.

As shown in FIGS. 7A and 7B, a frame F may be used to make chipresistor. The frame F is formed by punching a flat metal plate, forexample. The frame F includes a plurality of strips 11 elongated in apredetermined direction and a rectangular supporting portion 12 forsupporting the plurality of strips 11. Each of the strips 11 is flankedby slits 13. The strip 11 is connected to the supporting portion 12 viaconnecting portions 14 having width W1 smaller than the width W2 of eachstrip 11. Due to this structure, the connecting portions 14 are twistedto rotate the strip 11 through 90 degrees in an arrow N1 direction, tofacilitate process steps where solder layers 4′ or third insulatinglayers 33′ are formed on side surfaces 11 c of the strip 11, asdescribed later.

As shown in FIGS. 8A and 8B, a first surface 11 a of each strip 11 ofthe frame F is formed with a strip-shaped first insulating layer 31′sandwiched by two rows of strip-shaped conductive layers 21′. Similarly,a second surface 11 b opposite to the first surface 11 a of each strip11 is formed with a strip-shaped insulating layer 32′ sandwiched by tworows of strip-shaped conductive layers 22′ (the conductive layers 21′,22′ are represented by crisscross hatching in FIGS. 8A and 8B, as wellas in FIG. 9). Next, a pair of side surfaces 11 c of the strip 11 areformed with solder layers 4′. The solder layers 4′ may be formed tocover the surface of the conductive layers 21′, 22. Through the processsteps as described above, a bar-shaped resistor aggregate R3′ is made.Then, the resistor aggregate R3′ is cut along imaginary lines C3 to makea plurality of chip resistors R3. Each of the chip resistors R3 has asimilar structure as the chip resistor R1 illustrated in FIGS. 1 and 2.

Differing from the above methods, the chip resistor may be made by amethod illustrated in FIG. 9. Specifically, the first surface 11 a ofeach strip 11 of the frame F is provided with alternating formations ofrectangular insulating layers 31′ and conductive layers 21′. Similarly,the second surface 11 b opposite to the first surface 11 a is providedwith alternating formations of rectangular insulating layers 32′ andconductive layers 22′. Next, the pair of side surfaces 11 c of the strip11 are formed with insulating layers 33′. Through such process steps, abar-shaped resistor aggregate R4″ is made. Then, the resistor aggregateR4″ is cut along imaginary lines C4 to make a plurality of chipresistors R4′ which are not provided with the solder layers. Thereafter,a pair of end surfaces 1 c of the resistor element 1 of the chipresistor R4′ are plated with solder. In this way, a chip resistor R4 ismade to have a structure similar to the chip resistor R2 shown in FIG.6.

The solder layer 4 may be formed by barrel-plating, for example. Afterthe forming process of the plurality of chip resistors R4′, the chipresistors R4′ are placed all together in a single barrel to be platedwith solder. Each chip resistor R4′ has the end surfaces 1 c of theresistor element 1, the surfaces of main electrodes 21 and the surfacesof auxiliary electrodes 22 as exposed metallic surfaces. On the otherhand, the other surfaces are covered by the first to third insulatinglayers 31-33, whereby the solder layers 4 are appropriately formed overthe above-described metallic surfaces. Thus, the chip resistor R4 can bemade efficiently.

In the present invention, a plurality of chip resistors are made of oneplate. In the above-described embodiments, the plate is divided into theplurality of chip resistors by cutting. However, the plate may bedivided into the plurality of chip resistors by punching, for example.

In the present invention, the pairs of electrodes may be formed on onesurface of the resistor element. In this case, one pair of electrodesmay be used to detect an electric current while the other pair ofelectrodes may be used for voltage detection. Further, the spacingbetween the main electrodes may be equal to the spacing between theauxiliary electrodes.

The present invention being thus described, it is obvious that the samebay be modified in various ways. Such modifications should not beregarded as a departure from the spirit and scope of the invention, andall such modifications as would be obvious to those skilled in the artare intended to be included in the scope of the appended claims.

1. A chip resistor comprising: a resistor element including a first surface and a second surface opposite to the first surface; at least two main electrodes spaced from each other and provided on the first surface; and at least two auxiliary electrodes spaced from each other and provided on the second surface, the auxiliary electrodes facing the main electrodes via the resistor element; wherein the main electrodes and the auxiliary electrodes are made of a same material.
 2. The chip resistor according to claim 1, wherein a spacing distance between the auxiliary electrodes is no smaller than a spacing distance between the main electrodes.
 3. The chip resistor according to claim 1, further comprising a first insulating layer and a second insulating layer formed on the resistor element, wherein the first insulating layer covers an area between the main electrodes on the first surface of the resistor element, and the second insulating layer covers an area between the auxiliary electrodes on the second surface of the resistor element.
 4. The chip resistor according to claim 3, wherein a thickness of the first insulating layer is no greater than a thickness of the main electrodes.
 5. The chip resistor according to claim 1, further comprising at least two solder layers formed on the resistor element, wherein the resistor element includes a pair of end surfaces spaced from each other, each of the end surfaces being covered by a corresponding one of the two solder layers.
 6. The chip resistor according to claim 5, the solder layers cover the main electrodes and the auxiliary electrodes in addition to the end surfaces of the resistor element.
 7. The chip resistor according to claim 3, further comprising a third insulating layer formed on the resistor element, wherein the resistor element includes a side surface extending between the first surface and the second surface, the side surface being covered by the third insulating layer.
 8. A method of making a chip resistor, the method comprising the steps of: preparing a resistor material including a first surface and a second surface opposite to the first surface; forming a pattern of first conductive layer on the first surface; forming a pattern of second conductive layer on the second surface; and dividing the resistor material into a plurality of resistor elements; wherein the first conductive layer and the second conductive layer are made of a same material.
 9. The method of making chip resistor according to claim 8, wherein the dividing of the resistor material is performed in a manner such that a resulting chip resistor comprises a main electrode made of a part of the first conductive layer and also comprises an auxiliary electrode made of a part of the second conductive layer.
 10. The method of making chip resistor according to claim 8, further comprising an additional step, performed before the pattern forming of the first conductive layer, for forming a pattern of a first insulating layer on the first surface of the resistor material and also a pattern of a second insulating layer on the second surface of the resistor material, wherein the first conductive layer and the second conductive layer are formed on areas of the resistor material where the first and the second insulating layers are not formed.
 11. The method of making chip resistor according to claim 10, wherein the pattern forming of the insulating layer is formed by thick-film printing.
 12. The method of making chip resistor according to claim 10, wherein the first conductive layer and the second conductive layer are formed by metal plating.
 13. The method of making chip resistor according to claim 8, wherein the resistor material is divided by punching or by cutting.
 14. The method of making a chip resistor according to claim 8, further comprising the steps of: forming an insulating layer on a side surface of each resistor element; and forming a solder layer on an end surface of the resistor element by barrel-plating. 